2010’s Due Date hung its hopes on the Plains, Trains formula and after a promising first half hour, crashed and burned as a bland and annoying rethread. The formula is simple, the strict, play-by-the-rules, no-nonsense “straight man” has to, for one cockamamie reason or another, embark on a long and perilous trip with the kooky, annoying and impulsive bundle of energy, or the “comedy talent”.

With these films the formula is always there but at the end of the day, it’s the quality of the ingredients that really matter. The said comedy talent needs to be able to expose him or herself as a vulnerable human being with considerable chops in dramatic acting as well as his or her ability to act like a total goofball. If this character starts off as nothing but a caricature and continues this way until the end, the joke will eventually become stale. As much as I think Zach Galafianakis is a very inventive comedian, he can’t strip himself from acting as anything but a buffoon and was the wrong choice for Due Date.

On the other hand, John Candy was a master in performing the tightrope act between broad physical humor and honest, heartfelt character work. Melissa McCarthy, who was rightfully upgraded to lead status after her perfect bit in Bridesmaids (Let’s face it, she was pretty much the only reason to sit through that movie) is pretty close to reaching the comedy bar that was set pretty high by Candy.

McCarthy’s performance as the nasal-voiced, crass, rude, violent and sociopathic identity thief creates one of the most deplorable characters in recent history. But just when we are certain that this creature cannot be rehabilitated in any way, McCarthy manages to pull off a 180 like a comedy magician and challenges our prejudices. Honestly, if this role went to any other comedienne, I don’t think the film would be able to withstand such an abrupt change of characterization.

Take a look at the first act and the way McCarthy takes the red-haired white-trash caricature who beats up anyone who’s a threat with a swift karate chop and portrays her with brave comedic gusto and utmost raunchiness. On the other hand, you might be surprised to find yourself tearing up when she pours out her heart to Sandy (Justin Bateman), the person whose identity she stole, at a five star restaurant.

For a truly talented comedian to hit these completely different notes as perfectly as she did is a miracle, it doesn’t happen very often. Just think, how long has it been since John Candy died and who came close to his brand of warmth since then? When was the last time Bill Murray made one of those films where he starts off as a despicable person and eventually turns into a compassionate human being? Groundhog Day came out twenty years ago.

Is Identity Thief a mediocre action-comedy and am I cutting it too much slack because of McCarthy’s performance? I confess that there’s some truth to that. Jason Bateman presents a serviceable straight man, as he always does.

This time we’re in Midnight Run territory and director Seth Gordon (Horrible Bosses) relies on too many unnecessary car chases. Also, there are way too many antagonists in the story and the roster of bad guys becomes confusing after a while.

But it’s obvious that McCarthy is the true star here. If you miss the “scoundrel or parasite in the first half, angel in the second” comedies of John Candy, Bill Murray or Steve Martin, you’ll feel right at home.